Putative pheromone is simply another name for "unnamed" molecule, which has proven (or is being tested) to check for any type of effect on behavior.
Originally, this was offered by Androtics Direct (yep, same people who completely ruined A314, and lied on Pherotalk about it). Because of their "funny business" and bizarre charade of being a research company... many people are now looking to alternatives to their putative pheromones lineup.
Why charade you say? Well, many of these "secret" molecules are already known by their actual pheromone/chemical names. Some of them are also substances which are not exactly "natural" pheromones, however, they do have chemical structures which are similar to pheromones and proven themselves to have social or sexual effects.
... and while they claim to be a "research" company, they have yet to disclose the actual pheromones behind the putatives line - even after years of testing and reporting from users.
This was the entire purpose of testing and reporting in the first place.
Frankly, I wouldn't buy from them simply because of the type of sketchy antics they get up to (just read this article if you haven't already).
Like blocking people for talking about their products negatively, pulling products off the shelves, and never putting any of their experimental products on the main product line.
They simply disappear with no explanation or reason.
But before I go off on another rant about their business "politics", let me just say that I was fond of a few putative/experimental molecules they had on offer.
PheromoneXS in particular has been leading the way in providing excellent alternatives, although they aren't the only vendor in the game.
The reason PheromoneXS is such a big player is because SteveO, used to work for Androtics Direct in the past. I'm not sure of the reasons he quit, but I suspect he knew that they were lying to their customers. Androtics Direct is known for shilling on their forums and making it sound as if they're dealing with the most potent chemicals in pheromone-world... like real life pheromone love potions or something. But that's just not how they work.
In all my dealings with SteveO, he's been extremely trustworthy and always has top notch customer service. Product quality wise, as well as dealing with queries, requests, and after sales support.
You can also get singles from Liquid Alchemy Labs and Love Scent, both of which I recommend highly.
Note that several of the putatives have simply been wiped off planet pheromone, with no explanation about why they can't stock the item anymore. That's why not ALL the putatives currently have direct alternatives.
Also keep in mind that these molecules are nothing special. You can find many similar molecules which have been tested and proven in the human pheromone molecules summary. However, as always, I advise not looking to pheromone products as answers to all your problems. You can go crazy from trying to figure out all the effects and come up with something "extreme"...
But also keep in mind that you should also focus on building up a nice natural pheromone signature by keeping healthy.